Physical medium dependent layer bonding

ABSTRACT

A first protocol stack for communication on a first physical line is implemented. At least parts of a second protocol stack for communication on a second physical line are implemented. The first protocol stack and the second protocol stack are bonded at the Physical Medium Dependent layer of the first protocol stack and the Physical Medium Dependent layer of the second protocol stack ( 172 ). In some scenarios, the bonding may be at an upper edge of the Physical Medium Dependent layer, i.e., at the δ interface.

TECHNICAL FIELD

Various embodiments relate to a method of bonding physical lines at amodem and to a corresponding device. In particular, various embodimentsrelate to techniques of bonding a first protocol stack and a secondprotocol stack at the Physical Medium Dependent layer.

BACKGROUND

According to International Telecommunications Union (ITU)Telecommunications standard (ITU-T) G.998.2 (2005) bonding of aplurality of physical lines is located in between the physical layer(layer 1) and the data link layer (layer 2) at the γ interface.

Bonding above the physical layer or at an upper edge of the physicallayer has certain restrictions and drawbacks. E.g., it can be requiredto provide differential delay compensation buffers to cope with therequired differential delay of up to 10 milliseconds for high bit rates.In particular, big differential delay compensation buffers may berequired in a scenario where 10 ms impulse noise impacts one of thebonded physical lines, but not other bonded physical lines.

A further drawback is that adding another physical line to a bondinggroup can be comparably slow. Thus, switching between bonded mode andunbonded mode may not be possible or only possible to a limited degreeduring Showtime.

Further limitations and drawbacks relate to operation of the variousphysical lines in different modes. E.g., within existing referenceimplementations of bonding, operation may be limited to either fullpower transmission for all bonded physical lines or low power mode forall bonded physical lines. A combination of full power mode for one morebonded physical lines on the one hand side, with low power mode forfurther bonded physical lines on the other hand side may not be possibleor only possible to a limited degree.

A further drawback of existing reference implementations of bondingrelates to additional bonding overhead introduced. The bonding overheadreduces the throughput of applications implemented on the physical linesof a bonded group. E.g., fragmentation using sequence numbersidentifying fragments may be used for distributing data between bondedphysical lines; sequence numbers may require additional overhead.

SUMMARY

Therefore, a need exists for advanced techniques of bonding. Inparticular, a need exists for techniques which overcome or mitigate atleast some of the above-identified drawbacks and restrictions.

This need is met by the features of the independent claims. Thedependent claims define embodiments.

According to various embodiments, a method of bonding physical lines ata modem is provided. The method comprises implementing a first protocolstack for communication on a first physical line and implementing atleast parts of a second protocol stack for communication on a secondphysical line. The method further comprises bonding the first protocolstack and the second protocol stack at the Physical Medium Dependentlayer of the first protocol stack and at the Physical Medium Dependentlayer of the second protocol stack.

According to various embodiments, a device is provided. The devicecomprises a first interface configured to communicate on a firstphysical line. The device further comprises a second interfaceconfigured to communicate on a second physical line. The device furthercomprises at least one processor configured to implement a firstprotocol stack for communication on the first physical line via theinterface. The at least one processor is further configured to implementat least parts of a second protocol stack for communication on thesecond physical line via the second interface. The at least oneprocessor is configured to bond the first protocol stack and the secondprotocol stack at the Physical Medium Dependent layer of the firstprotocol stack and at the Physical Medium Dependent layer of the secondprotocol stack.

According to various embodiments, a computer program product isprovided. The computer program product comprises program code that canbe executed by at least one processor. Executing the program code by theat least one processor causes the at least one processor to execute amethod. The method comprises implementing a first protocol stack forcommunication on a first physical line and implementing at least partsof a second protocol stack for communication on a second physical line.The method further comprises bonding the first protocol stack and thesecond protocol stack at the Physical Medium Dependent layer of thefirst protocol stack and at the Physical Medium Dependent layer of thesecond protocol stack.

It is to be understood that the features mentioned above and those yetto be explained below may be used not only in the respectivecombinations indicated, but also in other combinations or in isolationwithout departing from the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, various embodiments are explained in further detailwith respect to the accompanying drawings.

FIG. 1 is a schematic illustration of two modems connected via a firstphysical line and a second physical line.

FIG. 2 is a schematic illustration of a physical layer and a data linklayer of a protocol stack for communication on one of the physical linesaccording to FIG. 1, wherein the physical layer implements a PhysicalMedium Dependent layer according to various embodiments.

FIG. 3 schematically illustrates at greater detail the physical layer offirst and second protocol stacks implemented for communication on thefirst and second physical lines, respectively, wherein FIG. 3illustrates a first mode where said bonding of the first and secondprotocol stacks is not executed according to various embodiments.

FIG. 4 generally corresponds to FIG. 3, wherein FIG. 4 illustrates asecond mode where said bonding is executed according to variousembodiments.

FIG. 5 schematically illustrates messages communicated between thePhysical Medium Dependent layer and an upper layer of the protocol stackwhich is above the Physical Medium Dependent layer according to variousembodiments.

FIG. 6 schematically illustrates the messages of FIG. 5 at greaterdetail, wherein the messages comprise a management section and acombined payload and management section and wherein FIG. 6 furtherillustrates splitting the messages to distribute fractions of themessages between the first and second protocol stacks according tovarious embodiments.

FIG. 7 generally corresponds to FIG. 6 and illustrates furtherembodiments.

FIG. 8 generally corresponds to FIG. 6 and illustrates furtherembodiments.

FIG. 9 generally corresponds to FIG. 6 and illustrates furtherembodiments.

FIG. 10 illustrates tone indices of bits of the messages, the toneindices associating the bits with tones of multitone symbols transmittedon either the first physical line or the second physical line accordingto various embodiments.

FIG. 11 schematically illustrates distributing of messages received fromthe upper layer of the first protocol stack above the Physical MediumDependent layer at greater detail according to various embodiments.

FIG. 12 generally corresponds to FIG. 11 and illustrates furtherembodiments.

FIG. 13 generally corresponds to FIG. 11 and illustrates furtherembodiments.

FIG. 14 schematically illustrates a device according to variousembodiments.

FIG. 15 is a flowchart of a method of bonding physical lines at a modemaccording to various embodiments.

FIG. 16 is a flowchart of a method according to various embodiments.

DETAILED DESCRIPTION OF EMBODIMENTS

In the following, embodiments will be described in detail with referenceto the accompanying drawings. It is to be understood that the followingdescription of embodiments is not to be taken in a limiting sense. Thescope of the invention is not intended to be limited by the embodimentsdescribed hereinafter or by the drawings, which are taken to beillustrative only.

The drawings are to be regarded as being schematic representations andelements illustrated in the drawings are not necessarily shown to scale.Rather, the various elements are represented such that their functionand general purpose become apparent to a person skilled in the art. Anyconnection or coupling between functional blocks, devices, components,or other physical or functional units shown in the drawings or describedherein may also be implemented by an indirect connection or coupling. Acoupling between components may also be established over a wirelessconnection. Functional blocks may be implemented in hardware, firmware,software, or a combination thereof.

Hereinafter, various techniques of bonding multiple physical lines aredisclosed. E.g., by bonding the multiple physical lines, Ethernettransport may be distributed across the multiple physical lines, therebyfacilitating high traffic throughput of communication between atransmitter modem and a receiver modem. Sometimes, bonding is alsoreferred to as aggregating multiple physical lines.

Techniques disclosed herein may be applied to various kinds oftransmission protocols. A particular focus is put, hereinafter, ontransmission according to the ITU-T G.9701 G.fast protocol forillustrative purposes only. Respective techniques may be readily appliedto other kinds of communication protocols, including, but not limited toITU-T G.992.X (ADSL and ADSL 2+), G.993.1 (VDSL1), and G.993.2 (VDSL2).Respective techniques may also be applied to non-DSL communicationprotocols; examples include the Institute of Electrical and ElectronicsEngineers (IEEE) 802.11 Wireless Local Area Network (WLAN) communicationprotocol and the Third Generation Partnership Project (3GPP) Long-TermEvolution (LTE) or Universal Mobile Telecommunications system (UMTS)protocol. Further examples include Bluetooth and satellitecommunication.

E.g., the various techniques disclosed herein can be applicable forcommunication system employed for the Internet of Things (IoT) where alarge number of devices communicates. Here, high traffic throughput, lowenergy consumption, and flexibility in operation modes may be ofbenefit.

According to embodiments, bonding of first and second protocol stacks isimplemented at the Physical Medium Dependent (PMD) layer of the firstand second protocol stacks. In some examples, bonding is done at the δinterface which corresponds to an upper edge of the PMD layer of thefirst and second protocol stacks.

Bonding at the upper edge of the PMD layer has particular advantages fortime-synchronized physical lines as are typically present for G.fast. Insuch a scenario, symbol boundaries—e.g., discrete multitone (DMT) symbolboundaries—in different physical lines are aligned in time domain and,furthermore, time positions of synchronization symbols in differentphysical lines are also aligned. Such a time-domain synchronization isparticularly present in vectored communication protocols such as ITU-TG.9701, G.993.2/G.998.4, as well as G.993.5.

A respective scenario is illustrated schematically by FIG. 1. FIG. 1illustrates a transmitter 101 and a receiver 111. The transmitter 101implements a first interface 105 configured to communicate via a firstphysical line 121. The transmitter 101 further implements a secondinterface 106 configured to communicate via the second physical line122. The receiver 111 implements a first interface 115 configured tocommunicate via the first physical line 121. The receiver 111 furtherimplements a second interface 116 configured to communicate via thesecond physical line 122.

While, with respect to FIG. 1, a scenario is illustrated where thecommunication on the first and second physical lines 121, 122 isimplemented as uni-directional communication, in other scenariosbi-directional communication may be readily employed. E.g., in somescenarios, bi-directional communication in, both, upstream (US) anddownstream (DS) may be implemented in frequency division duplexing (FDD)and/or time division duplexing (TDD) modes.

It is possible that the first physical line 121 is a first copper wirepair and that the second physical line is a second copper wire pair.E.g., the first and second physical lines 121, 122 may be integratedinto a single cable having a so-called quad-structure. Typically, for acable having the quad-structure, a comparably strong crosstalk betweenthe pairs of wires implementing the first and second physical lines 121,122 may be present; at the same time, a strongly reduced crosstalk maybe present between different cables having quad-structure. A shieldingeffect to the outside of the cable may be achieved. Employing both wirepairs of a cable for a single subscriber in a coordinated fashion cansubstantially improve the traffic throughput of the overallcommunication system; here, bonding may facilitate such a coordinatedcombination of communication.

Turning to FIG. 2, details of the protocol stacks implemented for acommunication on the first and second physical lines 121, 122 areillustrated. FIG. 2 schematically illustrates a protocol stack that maybe used in order to operate according to the G.fast protocol. In otherexamples, other protocols may be employed. The protocol stack 170 ofFIG. 2 comprises a data link layer 190 and the physical layer 180. Theprotocol stack 170 may comprise further upper layers above the data linklayer 190 (not shown in FIG. 2 for simplicity). In particular, theprotocol stack 170 may be structured according to the Open SystemsInterconnection model (OSI model). E.g., the protocol stack 170 mayfurther comprise (in ascending order) a network layer, a transportlayer, a session layer, a presentation layer, and an application layer(all not shown in FIG. 2).

The data link layer 190 may implement various functionalities such as:protection of communication of data, e.g., by means of an AutomaticRepeat Request (ARQ) protocol; conversion between service data units andprotocol data units of, e.g., Ethernet or TCP/IP; multiplexing ofmultiple protocols atop the data link layer; etc. It is possible thatthe data link layer 190 comprises one or more (sub-)layers such as thelogical link control sublayer and the media access control sublayer (notshown in FIG. 2).

FIG. 2 further illustrates details of aspects of the physical layer 180.The physical layer 180 comprises three (sub-)layers 181-183. The lowestlayer is the PMD layer 183. The PMD layer controls communication ofindividual bits on the physical lines 121, 122. E.g., the PMD layer 183may access an analog front end (AFE) and generate transmission framescomprising a plurality of symbols by requesting corresponding data fromthe upper layers 181, 182. As such, it is possible that the sequence ofbits 224 output by the PMD layer 183 is modulated into a multitonesymbol transmitted on one of the physical lines 121, 122. Furtherfunctionality implemented by the PMD layer 183 may comprise elementsselected from the group comprising: modulation; signal coding; bitsynchronization; Forward Error Correction (FEC); bit interleaving orother channel coding; control of a bit rate, thereby influencing atraffic throughput; etc. It should be understood that in specifictechnical fields the lowest layer of the protocol stack 170 may belabelled differently than PMD.

The PMD layer 183 is delimited by the delta (δ) interface 187 from thePhysical Medium-specific Transmission Convergence layer (PMS-TC) 182.The δ interface 187, thus, is the upper edge of the PMD. E.g., thePMS-TC layer 182 may implement encapsulation functionality.

The PMS-TC layer 182 is delimited by the α interface 186 from theTransport Protocol-specific Transmission Convergence (TPS-TC) layer 181interfacing to the datalink layer 190 via the γ interface 185. E.g., theTPS-TC layer 181 may provide functionality selected from the groupcomprising: cell conversion; header error check (HEC) calculation;removing idle cell; descrambling of payload.

FIG. 3 illustrates aspects of a first mode 151 where bonding between afirst protocol stack 171 and a second protocol stack 172 is notexecuted. FIG. 3 is an example where the first and second protocolstacks 171, 172 operate according to the G.fast protocol.

In some examples, data may be communicated on the first physical line121 by means of the first protocol stack 171 independently of datacommunicated on the second physical line 122 by means of the secondprotocol stack 172. In particular, in such a scenario it is possiblethat the second protocol stack 172 is operated at Showtime in a firstmode 151, i.e., fully powered-up and communicating data on the physicalline 122. Such techniques may increase a traffic throughput.

In other examples, it is also possible that the second protocol stack172 is operated in a Showtime low power state or in a powered downstate. I.e., the Showtime low power state may correspond to a scenariowhere initialization of the second protocol stack 172 from the powereddown state has occurred, but—beyond some management data or controldata—payload data is not communicated via the second physical line 122.E.g., the second protocol stack 172 may generate idle bits and/orsynchronization symbols for communication on the second physical line122 in the first mode 151. Such techniques may reduce power consumption.

As illustrated with respect to FIG. 4, it is now possible to switch ortransition from the first mode 151—where bonding 301 is not executed—toa second mode 152 where bonding 301 is executed. Switching may occurduring training and/or during Showtime.

As can be seen from FIG. 2, the bonding 301 is at the upper edge 187A,187B of the PMD layer 183. Bonding 301 can be implemented usingtime-synchronous operation—i.e., boundaries of symbols communicated viathe first and second physical lines 121, 122 being in time domain—suchthat whenever a message is communicated over the upper edge of the PMDlayer 183 of the first protocol stack 171 (labeled in FIG. 4 as δ2interface 187B) a corresponding message 223B is communicated over theupper edge/δ2 interface 187B of the PMD layer 183 of the second protocolstack 172. To achieve this, the bonding 301—implemented at the upperedge of the PMD layer 183—comprises distributing messages 223 receivedfrom the layer 182 between the first protocol stack 171 and the secondprotocol stack 172. In FIG. 4, said distributing is implemented by afunctional/logical entity labelled δ aggregation function (DAF). FIG. 4illustrates that the original δ interface 187 has been split into the δ1interface 187A and the δ2 interface 187B due to the insertion of theDAF.

Implementing techniques of bonding 301 at the PMD layer 183, e.g., asillustrated with respect to FIG. 4 has certain effects. First, byimplementing said bonding 301 at the low PMD layer 183, it is possibleto enable/disable said bonding 301 on-the-fly during Showtime. E.g., insome examples it is then possible to switch between the first mode 151and the second mode 152 depending on a traffic load and a trafficthroughput of communication on the first physical line 121 via the PMDlayer 183 of the first protocol stack 171. E.g., if the traffic loadexceeds a certain predefined threshold, the second mode 152 may beselectively enabled. The predefined threshold may be dependent on thetraffic troughput of the PMD layer 183 of the first protocol stack 171.

Further, additional memory—as may be required in referenceimplementation where bonding is executed at an upper layer 181, 182,190—may not be required or only be required to a limited degree.

Further, by implementing the bonding 301 according to techniquesdisclosed herein, traffic throughput/bit rate capabilities can beincreased. E.g., it can be possible to implement a traffic throughput of1 Gbit per second over comparably long physical lines 121, 122 whenimplementing a G.fast protocol. E.g., such traffic throughput may beachieved for a length of the physical lines 121, 122 of up to 250meters. In particular, by said bonding 301, it can be possible to doublethe available traffic throughput over a given length of the physicallines 121, 122.

If compared to reference implementation, a complexity can be reduced,e.g., due to a reduced size of required memory buffers.

Further, in a scenario where quad-structure cables com are relied upon,a particular improvement of efficiency can be achieved by bonding 301the two wire pairs implementing the physical lines 121, 122 due tocoordinated communication via both wire pairs.

Now referring again to FIGS. 3 and 4, details of operation will beexplained. As mentioned above, there are two physical lines 121, 122associated with a transmitter and receiver 101, 111. Both thetransmitter 101 and the receiver 111 implement PMD layers 183, each PMDlayer 183 associated with the two protocol stacks 171, 172. The TPS-TC,PMS-TC layers 181, 182 of the first protocol stack 171 arepermanently—i.e., independently of the first or second mode of operation151, 152—connected with the PMD layer 183 of the first protocol stack171. The TPS-TC layer 181 is connected to a user traffic/payload data atthe γ interface 185. The payload data may originate from higher layersabove the physical layer 180. Because of this, the first protocol stack171 is operating as so-called master or bonding master. Differently, thesecond protocol stack 172 operates as slave or bonding slave. Inparticular, the master protocol stack 171 controls operation of the PMDlayers 183 of, both, the first and second protocol stacks 171, 172. Inparticular, the messages 223 crossing the lower edge of the layer182/the δ1 interface 187A are distributed between the PMD layers 183 ofthe first and second protocol stacks 171, 172. In particular, the secondprotocol stack 172 only implements the PMD layer 183 in the second mode152; the TPS-TC, PMS-TC layers 181, 182 are not required and used (and,therefore, not shown in FIG. 4).

FIG. 3 illustrates a situation during unbonded first mode 151. Here, thefirst protocol stack 171 communicates payload data. This comprisestransmitting payload data across the γ interface 185 to PMD 183 of thefirst protocol stack 171 and receiving payload data from the physicalline 121, processing it at the PMD layer 183 as well as at the TPS-TC,PMS-TC layers 181, 182 and passing the payload data across the γinterface towards the data link layer 190 in reverse direction. In theunbonded first mode 151, it is not required that the second protocolstack 172—acting as slave—transmits or receives any payload data;therefore, the second protocol stack 172 doesn't have to be powered infull. The second protocol stack 172 may even be powered down.

Using the unbonded first mode is possible as long as the trafficthroughput of the first protocol stack 171 is sufficient for theapplication speed/the traffic load. Where the traffic throughput becomesinsufficient, a part of the traffic is distributed to the secondprotocol stack 172, in the second mode 152 (cf. FIG. 4). For that, thesecond protocol stack has to achieve full operation bit rate within areasonable timeframe of, e.g., 1-2 seconds. E.g., for this, it canbecome possible to transition the second protocol stack 172 from apowered down state or a Showtime low power state to Showtime. Then, thebonding 301 can be executed in response to initializing the secondprotocol stack 172 into Showtime, e.g., from powered down mode orShowtime low power mode.

Now referring to FIG. 5, aspects regarding the data exchange across theδ interface 187, 187A, 187B are illustrated. In particular, FIG. 5illustrates distributing messages 223 between the first and secondprotocol stacks 171, 172.

Typically, the data exchange at the δ interface 187, 187A, 187B is donevia so-called “data frames” according to reference implementation. FIG.5 illustrates a data frame message 223 being an ordered set of bits orbytes that can be modulated to, e.g., exactly a single DMT symbol forcommunication on a physical line 121, 122. A data frame message 223 canbe seen as a row vector with one entry for each bit. Thus, according toreference implementations, for every transmit DMT symbol—exceptsynchronization symbols—the respective PMD layer 183 requests a dataframe message 223 which is delivered by the PMS-TC layer 182; likewise,for every receive DMT symbol—except synchronization symbols—the PMDlayer 183 delivers a data frame message 223 to the PMS-TC layer 182.

During operation, the data frame messages 223 of the first protocolstack 171 carry payload data and/or management data, whereas the dataframe messages 223 of the second protocol stack 172, in the unbondedfirst mode 151, do not carry payload data or management data, but arefilled up with idle bits or dummy bits.

Illustrated in FIG. 5, upper part is a situation where the data framemessage 223 comprises four bits. When operating in the unbonded firstmode 151, the data frame message 223 communicated across the lower edgeof the PMS-TC layer 182/the δ1 interface 187A is the same as the dataframe message 223 communicated across the upper edge of the PMD layer183/the δ2 interface 187B. Thus, in the unbonded first mode 151, thetransmit data frame message 223 generated by the PMS-TC layer 182 of thefirst protocol stack 171 is identical to the transmit data frame messagepassed to the PMD layer 183 of the first protocol stack 171.

Next, the situation of the bonded second mode 152. In the bonded secondmode 152 the second protocol stack 172 is powered and the DAF bonds thePMD layer 183 of the first protocol stack 171 and the PMD layer 183 ofthe second protocol stack 172, e.g., as slave to the master firstprotocol stack 171. The transmit data frame messages 223 of the PMS-TClayer 182 of the first protocol stack 171 are distributed between thefirst protocol stack 171 and the second protocol stack 172, inparticular between the PMD layer 183 of the first protocol stack 171 andthe PMD layer of the second protocol stack 172. Likewise, data framemessages 223 comprising data received via one of the physical lines 121,122 are bonded, e.g., by the DAF, and passed to the layer 182 of thefirst protocol stack 171.

In the bonded second mode 152, in some examples, any transmit data framemessage 223 generated by the PMS-TC layer 182 of the first protocolstack 171 is distributed either to the PMD layer 183 of the firstprotocol stack 171 or to the PMD layer 183 of the second protocol stack172.

In particular in such an example, it is possible to flexibly adapt theamount of data distributed to the first protocol stack 171 in comparisonto the amount of data distributed to the second protocol stack 172(bonding strength). This may be implemented by distributing everysecond, third, fourth, etc. transmit data frame message 223 to thesecond protocol stack 172 for transmission on the second physical line122. E.g., the bonding strength may be adjusted depending on at leastone of the traffic load and the traffic throughput of the communicationon the physical line 121. To facilitate time-synchronized transmissionthe PMD layer 183 of the second protocol stack 172 may fill uptransmission frames with idle bits where required.

In FIG. 5, lower part, a further example is shown. Here, a data framemessage 223 generated by the PMS-TC layer 182 of the first protocolstack 171 is a concatenation of a first fraction 223A corresponding tothe data frame message to be passed to the PMD layer 183 of the firstprotocol stack 171—and a second fraction 223B corresponding to the dataframe message to be passed to the PMD layer 183 of the second protocolstack 172. This corresponds to a vectored concatenation of to rowvectors as illustrated in the lower part of FIG. 5. In such a scenario,the distributing comprises splitting at least some of the messages 223to distribute the fractions 223A, 223B of the messages 223 between thefirst protocol stack 171 and the second protocol stack 172. Inparticular, in such a scenario the distributing may depend on a positionof the fractions 223A, 223B of the messages 223 within each message 223.E.g., in the example illustrated in the lower part of FIG. 5, thefraction 223A associated with the PMD layer 183 of the first protocolstack 171 is located in the beginning of the message 223, i.e., at themost significant bit, while the fraction 223B associated with the PMDlayer 183 of the second protocol stack 172 is located at the end of thedata frame message 223, i.e., at the least significant bit. In otherexamples, the reverse order is conceivable where the fraction 223Aassociated with the PMD layer 183 of the first protocol stack 171 islocated at the least significant bit.

With respect to FIG. 5 above, a specific rule for distributing the dataframe messages 223 between the first and second protocol stacks 171, 172has been illustrated. In the various scenarios disclosed herein, it ispossible to implement various kinds and types of rules of saiddistributing. E.g., such rules of distributing the data frame messages223 can be predefined or can be negotiated/aligned between thetransceivers 101, 111 during startup or during Showtime when switchingbetween the first mode 151 and the second mode 152. E.g., respectivecontrol data indicating such a predefined rule may be communicated on atleast one of the first physical line 121 and the second physical line122, e.g., in response to switching between the first mode 151 and thesecond mode 152.

Hereinafter, some examples are given of specific rules of distributingthe data frame messages 223 between the first and second protocol stacks171, 172.

In a first example, all data frame messages 223 are distributed betweenthe first and second protocol stacks 171, 172, e.g., in alternatingorder or using a different pattern having a weaker bonding strength.

In a second example, all data frames having indices larger than zero(the indices corresponding to a position of a transmission frame) aredistributed between the first and second protocol stacks 171, 172, e.g.,in alternating order or using a different pattern. Here, data frameshaving index zero in the transmission frame may all be assigned toeither the first protocol stack 171 or the second protocol stack 172.Data frame messages 223 having index zero in the transmission frame aretypically positioned at the beginning of the transmission frame.Typically, data frame messages 223 having index zero carry a dedicatedmanagement section including management information for the firstprotocol stack 171 and/or the second protocol stack 172. Concerning thedistributing between the first and second protocol stacks 171, 172, incase of G.fast it is typically distinguished between the synchronizationsymbols which are transporting no data frame messages 223, data symbolswhich are transporting data frame message 223 with index larger thanzero and RMC symbols which are transporting data frame messages 223 withindex zero. The various indices of the data frame messages are alsoillustrated by FIG. 9-3 of G.9701 (Dec. 5, 2014).

With regard to the G.fast protocol, examples of management informationcomprise the Robust Management Channel (RMC) and the embedded operationschannel (eoc) which is typically carried in a combined management andpayload section. In particular, management information such as the RMCor the eoc may be determined by one of the upper layers 181, 182.Management information for the first protocol stack 171 or the secondprotocol stack 172 may comprise elements selected from the groupcomprising: TDD framing parameters; Showtime Adaptive Rate (SAR)parameters; and vectoring error reports.

Now turning to FIG. 6, various aspects with respect to distributing ofthe data frame messages 223 received from the layer 182 between the PMDlayer 183 of the first protocol stack 171 and the PMD layer 183 of thesecond protocol stack 172 are illustrated. In the scenario FIG. 6, adata frame message 223 is received which comprises a first managementsection 223-1 comprising management information for the first protocolstack 171 and comprising a second management section 223-2 comprisingmanagement information for the second protocol stack 172. E.g., the dataframe message 223 of FIG. 6 could have index zero, i.e., dedicated forthe beginning of a transmission frame. The data frame message 223further comprises a combined payload and management section whichcarries payload data and management information for the first protocolstack 171 and/or the second protocol stack 172. E.g., in the G.fastframework, the sections 223-1, 223-2 may correspond to the RMC while thesection 223-3 corresponds to the data transfer unit (DTU) used totransfer payload data bits and further comprising eoc managementinformation (not illustrated in FIG. 6).

The data frame message 223 is received from the PMS-TC layer 182 of thefirst protocol stack 171. I.e., that the management information for thesecond protocol stack 172 is also generated and transported by thelayers 181, 182 of the first protocol stack 171 in the bonded secondmode 152. In particular, in the G.fast framework, the eoc managementinformation indicates management information for, both, the firstprotocol stack 171 and the second protocol stack 172. Also, the TMS-TC,PMS-TC layers 181, 182 of the first protocol stack 171, in the G.fastframework, generate the RMC management sections indicating, both,management information for the first protocol stack 171 and the secondprotocol stack 172, respectively.

In the example of FIG. 6, the RMC management sections 223-1, 223-2 are,both, distributed to the first protocol stack 171 only, i.e., are notdistributed to the second protocol stack 172. Here, the fraction 223Awhich comprises the management sections 223-1, 223-2 are distributed tothe first protocol stack 171.

FIG. 7 illustrates a further scenario, where the RMC management sections223-1, 223-2 are distributed to, both, the first protocol stack 171 andthe second protocol stack 172. Here, the management section 223-1 (themanagement section 223-2) indicating management information for thefirst protocol stack 171 (the second protocol stack 172) iscommunication on the first physical line 121 (the second physical line122).

FIG. 8 illustrates a further scenario of distributing the data framemessages 223 between the first and second protocol stacks 171, 172. Inthe scenario of FIG. 8, only a single RMC management section 223-1 isincluded in the data frame message 223; e.g., the single RMC managementsection 223-1 may indicate management information for only one of thefirst or second protocol stacks 171, 172 or may indicate managementinformation for, both, the first and second protocol stacks 171, 172.

The scenario of FIG. 9 illustrates a further scenario where a data framemessage 223 has an index larger than zero, i.e., being positioned not infront of a transmission frame of the PMD layer 183; such a data framemessage 223 does not comprise any RMC management section 223-1, 223-2;but may include eoc management information.

In the various scenarios disclosed above, it may be helpful todistinguish between the management sections 223-1, 223-2 indicatingmanagement information for the first protocol stack 171 on the one handside, and the management sections 223-1, 223-2 indicating managementinformation for the second protocol stack 172 on the other hand side.For this purpose, it is possible that management information—such as RMCinformation or eoc information—includes special identification bits toenable differentiation between management information for the first andsecond protocol stacks 171, 172, respectively. Such control indicesimplemented by the identification bits may facilitate distinguishing thecontrol sections 223-1, 223-2 at the upper PMS-TC, TMS-TC layers 181,182. The control indices may also facilitate distributing between thefirst and second protocol stacks 171, 172.

In a further example, the management sections 223-1, 223-2 aredistinguished by the time position, respectively the position withineach data frame message 223. Such a scenario is conceivable in ascenario where transmission frames are associated with dedicated dataframe messages 223 or respective sections 223-1, 223-2 of data framemessages 223 as is the case for RMC management information. Such ascenario is in particular facilitated by time-synchronized physicallines 121, 122 of a bonding group. Distinguishing between managementinformation for the first and second protocol stacks 171, 172 based onthe time position of the received transmission frames may thus be onlypossible for a limited degree in the G.fast framework for eoc managementinformation which is communicated together with the payload data and hasits insertion/extraction allocation at the layer 181—unless a specialmapping of eoc management information aligned with DTU 223-3 boundariesand boundaries of the data frame messages 223 is used.

In still a further embodiment, tone indices of bits of the data framemessages 223 are used to distinguish between management information forthe first and second protocol stacks 171, 172, respectively. E.g., aconcept of so-called virtual tone indices may be employed where thevalue of the tone indices enables to distinguish between tones used forcommunicating on the first physical line 121 via the first protocolstack 171 and tones used for communicating on the second physical line122 via the second protocol stack 172. Also, the tone indices mayfacilitate the distributing between the first and second physical lines172, 172.

Such a scenario of tone indices is illustrated in FIG. 10 where thevarious tones of the multi-tone signals used for communicating on thephysical lines 121, 122 are illustrated in a constellation diagram.Respective indices may be used to judge which protocol stack 171, 172the respective section 223A, 223B of a data frame message 223 should bedistributed to. E.g., the virtual tone indices of the second protocolstack 172—operating as bonding slave—can correspond to the tone indicesof the first protocol stack 171—acting as bonding master—increased bythe highest tone index of the first protocol stack 171.

FIGS. 11-13 illustrate the distributing of data frame messages 223between the first and second protocol stacks 171, 171 at greater detail.Here, the PMD layer 183 of the first protocol stack 171 is labelled“PMDa” and the PMD layer 183 of the second protocol stack 172 islabelled “PMDb”. FIG. 11 shows a scenario where data frame messageshaving index zero and data frame messages 223 having indices larger thanzero are distributed. The data frame messages 223 having indices largerthan zero contain payload data bits only, whereas the data framemessages 223 having index zero contain, both, payload data bits and RMCmanagement bits.

Two examples are conceivable regarding distributing of the managementsection 223-1, 223-2 having RMC management information. First—asillustrated in FIG. 11—the management sections 223-1, 223-2 indicativeof RMC management information for, both, the first and second protocolstacks 171, 172 are transported via the PMD layer 183 of the firstprotocol stack 171, only. Such a scenario may be difficult to implementwhere management sections 223-1, 223-2 are present in each data framemessage 223, e.g., due to synchronization purposes, facilitatinglow-power mode, etc.

A second example as to implement two logical management channels, i.e.,to distribute the management sections 223-1, 223-2 between, both, thefirst and second protocol stacks 171, 172 (as illustrated in FIGS. 12and 13). Here, the first physical line 121 is used for communicatingmanagement sections 223-1, 223-2 indicating management information forthe first protocol stack 171; while the second physical line 122 is usedfor communicating management sections 223-1, 223-2 indicating managementinformation for the second protocol stack 172.

Now turning to FIG. 14, a device 501 is illustrated which may implementtechniques of bonding at the PMD layer 183 as disclosed herein. E.g.,the device 501 may implement the transmitter 101 and/or the receiver111. The device 501 comprises two AFEs 505, 506 for communicating on thephysical lines 121, 122, respectively. US and DS communication ispossible, e.g., in a TDD mode. The AFEs 505, 506 together with a digitalfront end (DFE) 502 implement the two interfaces 105, 115, 106, 116 ofthe transmitter 101 and/or the receiver 111, respectively. The DFE 502comprises a processor 512 and a memory 511. The memory 511 can storeprogram code that can be executed by the processor 512. Executing theprogram code causes the processor 512 to perform techniques as disclosedherein with respect to, e.g., bonding at the PMD layer 183, inparticular at the δ interface 187, distributing data frame messages 283to the first protocol stack 171 and/or the second protocol stack 172,splitting data frame messages 283, implementing the first protocol stack171, implementing the second protocol stack 172, etc. The device 501further comprises a human machine interface (HMI) 515 configured tooutput information to a user and configured to receive information froma user. The HMI 515 is optional.

FIG. 15 is a flowchart illustrating a method that may be executed by theprocessor 512. First, at 1001, the first and second protocol stacks 171,172 are implemented. Here, in particular, it is possible that all layers180, 190 and layers 181-183 are implemented for the first protocol stack171, but that only the PMD layer 183 is implemented for the secondprotocol stack 172 (cf. FIG. 4).

Next, at 1002, the first and second protocol stacks 171, 172 are bonded301 at the PMD layer 183. In particular, bonding may occur at the upperedge of the PMD layer 181, i.e., at the δ interface 187, 187A, 187B.

FIG. 16 is a flowchart of a method according to various embodiments.First, at 1011, the first protocol stack 171 and the second protocolstack 172 are initialized. During the start-up procedure, informationmay be exchanged between the transmitter 101 and the receiver 111.Respective control data may be communicated on at least one of the firstphysical line 121 and the second physical line 122 and may indicate aparameter of said bonding 301.

E.g., the control data may indicate, in a first example, whether aphysical line 121, 122 shall be a bonding master candidate or a bondingslave candidate during Showtime operation. In a second example,alternatively or additionally, the control data may indicate thedistribution bit order, i.e., whether the received data frame messages223 comprise fractions to be distributed to the first protocol stack 171at the most significant bit or at the least significant bit (asillustrated above with respect to FIG. 5). In a third example,alternatively or additionally, the control data may indicate thesize—e.g., in bits—and distribution order of data frame messages 223into the first and second protocol stacks 171, 172.

During start-up/training at 1011, it is possible to synchronize thecommunication on the first physical line 121 and the communication onthe second physical line 122 in time domain. In particular, generationof transmission frames by the physical media dependent layers 183 of thefirst and second protocol stacks 171, 172 may be synchronized in timedomain.

FIG. 16 illustrates a scenario where initially only the first protocolstack 171 is operated at Showtime, 1012. Differently, the secondprotocol stack 172 goes to a Showtime low power state afterinitialization from powered down state, 1013. I.e., initially, payloaddata is communicated on the first physical line 121 via the PMD layer171 of the first protocol stack 171, only. The second protocol stack 172is initialized into Showtime only later.

Next, at 1014, it is checked whether the traffic—which is currentlyrouted via the first protocol stack 171 only—exceeds a certainthreshold. Only if this is the case, switching from the first mode 151to the second mode 152 employing bonding 301 is executed. Thus, as canbe seen from FIG. 16, the power state of the second protocol stack171—which is now operated at Showtime, 1015, to facilitate the bonding301—is controlled depending on the traffic throughput demand and thebonding.

At 1017 it is checked whether the traffic throughput is still above thethreshold. If this is not the case, it is switched back from the secondmode 152 to the first mode 151 and bonding 301 is stopped.

As can be seen from the exemplary scenario of FIG. 16, it is possible toswitch from unbonded first mode 151 to bonded second mode 152 (bondingentry); it is also possible to switch back from bonded second mode 152to unbonded first mode 151 (bonding exit). In particular, it is possibleto switch back and forth from the first and second modes 151, 152 duringShowtime.

Switching between the modes 151, 152 can be controlled by upper layers190, 181, 182 above the PMD layer 183. In particular, the switching candepend on the traffic throughput of the applications delivering payloaddata. In particular, switching back and forth between the first andsecond modes 151, 152 can be implemented analogous to switching betweenlow-power mode and full-power mode according to the ITU-T G.9701.Whenever an application requires a higher traffic throughput thanoffered by the PMD layer 183 of the bonding master first protocol stack171, the first protocol stack 171 indicates to the higher layers 190,181, 182 that bonding 301 is required. Then, the higher layers 190, 181,182 initiate a bonding entry procedure. Whenever the applications do notrequire high traffic throughput anymore that is higher than trafficthroughput offered on the first physical line 121, only, the higherlayers 190, 181, 182 initiate the bonding exit procedure and switch backto the first mode 151. A certain hysteresis of switching between thefirst and second modes 151, 152 can be considered in time domain toavoid permanent toggling between the first and second modes 121, 122 fortraffic throughput varying close to the respective threshold.

Various scenarios are conceivable for aligning the switching between thefirst mode 151 in the second mode 152 in time domain. E.g., foralignment of the switching between the transmitter 101 and the receiver111, the point in time or time instant of each particular switching canbe coordinated via control data exchanged between the transmitter 101and the receiver 111. E.g., in the G.fast scenario, the eoc or the RMCcan be employed. In particular, exchange of control data can beimplemented analogous to reference implementations of onlinereconfiguration such as for SRA.

It is possible that switching between the first mode 151 and the secondmode 152 occurs between two time-division multiplex frames of the PMDlayer 183 and/or at a point in time corresponding to a synchronizationframe of the PMD layer 183. The synchronization frame may correspond toat least one synchronization symbol communicated on one of the physicallines 121, 122. Hence, it is possible that the time instant from whichthe new bonded or unbonded mode 151, 152 starts is the beginning of asuperframe, a particular logical frame, or a particular TDD frame. Fromthe start of a new bonded mode 152, the layer 182 starts to dispatchdata frame messages 223 in a manner as specified by a predefined rule ofdistributing. E.g., the layer 182 can dispatch data frame messages 223in a concatenated manner—i.e., comprising two individual data framemessages as sections 223A, 223B for distributing to the PMD layer 183 ofthe first protocol stack 171 or the second protocol stack 172,respectively (cf. FIG. 5, lower part). Since synchronization symbols donot carry payload data or other data included in the data frame message223 and are communicated on both physical lines 121, 122 at the samepoint in time, they can be used to mark a switching point. Inparticular, such a technique enables the receiver 111 to detect theswitching and implement changes to the mode of operation of the upperlayers 181, 182 and further implementing the DAF. E.g., the firstprotocol stack 171 can handle switching procedures between the modes151, 152 in a manner comparable to reference implementations withrespect to SRA or Fast Rate Adaptation (FRA). For sake of channelestimation, the PMD layer 183 of the second protocol stack 172 typicallysends synchronization symbols in both modes 151, 152.

With respect to FIG. 16, a scenario has been illustrated where switchingto the second mode 152 comprising bonding 301 is triggered by a requiredtraffic, 1014, 1017. In other examples, it is also possible toinitialize the second protocol stack 172 from a powered down state intoShowtime and execute bonding 301 in response to initializing the secondprotocol stack 172 into Showtime. I.e., in such a scenario it ispossible that the second mode 152 is activated automatically once thesecond protocol stack 172 has initialized into Showtime—irrespective ofthe traffic throughput. Here, the second protocol stack 172 implementingthe bonding slave is bonded to the first protocol stack 171 implementingthe bonding master immediately and autonomously after going to Showtime,e.g., at the first data frame message 223 of the first superframe.

In the various scenarios disclosed herein, examples have been givenwhere the first protocol stack 171 acts as a master with respect to thesecond protocol stack 172 implementing a slave. Various scenarios areconceivable for deciding which protocol stack 171, 172 acts as masterand slave, respectively. In one example, the protocol stack 171, 172acting as bonding master is defined by the PMD layer 183 which is goingfirst to Showtime after power up. Hence, it is possible that the firstprotocol stack 171 acting as master is initialized first into Showtimeand that only then the second protocol stack 172 is initialized intoShowtime.

Summarizing, above various techniques for bonding in the modem have beenillustrated, in particular for a modem having two pairs of wires, eachpair being coupled respectively to a master and slave module, wherein atleast one of the master and slave module has a TMS-TC layer 181 and thePMS-TC layer 182 coupled to a PMD layer 183 through a δ interface 187,187A, 187B, wherein the two pairs of wires are bonded at the PMD layer183. Here, it is possible that the master controls the two physicalmedia dependent layers 183 of the first and second protocol stacks 171,172, respectively. Time of bonding entry and bonding strength can beadjusted by upper layers 181, 182, 190, in particular by a trafficthroughput demand of applications implemented in upper layers 181, 182,190. The power of the protocol stack of the bonding slave can beadjusted by the time of the bonding entry and/or the bonding strength.

By the various techniques disclosed herein, effects can be achieved. Inparticular, dynamic switching between a bonded state and an unbondedduring Showtime is possible. The switching can occur within a timeduration corresponding to a single superframe. The switching can mimiconline reconfiguration according to reference implementation andtherefore enable simple implementation for the physical layer oftransmitter and receiver.

By the techniques disclosed herein, further, a higher traffic throughputcan be achieved, because bonding at the PMD layer typically does notrequire a significant bonding overhead to be communicated via thephysical lines. In particular, it is not required—as in referenceimplementation—to segment data as an upper layer and include respectivesequence numbers in the segmented data in order to facilitate datareassembly. Instead, the time-synchronized operation of the PMD layersof the first and second protocol stacks can be relied upon forreassembly.

A further effect is that power consumption can be significantly reduced.In particular, where operation in an unbonded first mode is sufficientin terms of required traffic throughput, protocol stacks implementingbonding slaves can be put into a low-power mode. This may beparticularly relevant for IoT applications.

Further, by implementing techniques of bonding as disclosed herein, itis typically not required to implement differential link delaycompensation buffers. This and other techniques disclosed herein reducethe complexity required. In particular, it is not required to implementsegmentation at the data link layer or an upper edge of the physicallayer—rendering it unnecessary to include respective segmentationsequence numbers. Further, it is not required to re-order segment anddata chunks by means of such sequence numbers. Further, at startup it isnot required to negotiate a special bonding function.

Although the invention has been shown and described with respect tocertain preferred embodiments, equivalents and modifications will occurto others skilled in the art upon the reading and understanding of thespecification. The present invention includes all such equivalents andmodifications and is limited only by the scope of the appended claims.

E.g., while various examples have been disclosed with respect to theG.fast protocol, it is possible to readily apply the respectivetechniques to other communication systems or protocols. In particular,respective techniques as disclosed herein may be readily applied tomultitone communication in time-synchronized physical lines. E.g., whilevarious scenarios have been disclosed with respect to wired physicallines, respective techniques may be readily applied to air interfaces.

E.g., while above various examples have been discussed with respect toUS, respective techniques may be readily applied to DS. Further, thetechniques disclosed herein are not limited to uni-directionalcommunication on the physical lines, but can be applied tobi-directional communication, e.g., in a TDD or FDD geometry.

Further, while above reference has been made to various specific layersof the physical layer such as the TMS-TC layer and the PMS-TC layer, inother scenarios, other kinds of layers of the physical layer may beimplemented. E.g., different terminology may be adapted for the layersby standards according to the ITU-T or the OSI.

1-26. (canceled)
 27. A method of bonding physical lines at a modem, themethod comprising: implementing a first protocol stack for communicationon a first physical line, implementing at least parts of a secondprotocol stack for communication on a second physical line, bonding thefirst protocol stack and the second protocol stack at the PhysicalMedium Dependent layer of the first protocol stack and at the PhysicalMedium Dependent layer of the second protocol stack.
 28. The method ofclaim 27, wherein said bonding is at an upper edge of the PhysicalMedium Dependent layer of the first protocol stack and an upper edge ofthe Physical Medium Dependent layer of the second protocol stack. 29.The method of claim 28, wherein the upper edge of the Physical MediumDependent layer is the delta interface.
 30. The method of claim 27,wherein said bonding comprises: receiving messages from an upper layerof the first protocol stack above the Physical Medium Dependent layer,the messages comprising at least one of a payload section, a managementsection, and a combined payload and management section, distributing themessages between the first protocol stack and the second protocol stack.31. The method of claim 30, wherein said distributing comprisessplitting at least some of the messages to distribute fractions of themessages between the first protocol stack and the second protocol stack.32. The method of claim 30, wherein at least those fractions of themessages comprising the management section and/or the combined payloadand management section are distributed to the first protocol stack, themanagement section and the combined payload and management sectionindicating management information for the first protocol stack and thesecond protocol stack.
 33. The method of claim 30, wherein saiddistributing depends on at least one of control indices of sections ofthe messages associated with the first protocol stack or the secondprotocol stack, tone indices of bits of the messages, the tone indicesassociating the bits with tones of multitone symbols transmitted oneither the first physical line or the second physical line, and aposition of fractions of the messages within each message.
 34. Themethod of claim 30, wherein said distributing depends on a predefinedrule.
 35. The method of claim 27, wherein the first protocol stackcomprises the Physical Medium Dependent layer and at least one upperlayer above the Physical Medium Dependent layer, wherein the secondprotocol stack comprises the Physical Medium Dependent layer and doesnot comprise the at least one upper layer above the Physical MediumDependent layer.
 36. The method of claim 27, wherein the first protocolstack is operated as master, wherein the second protocol stack isoperated as slave.
 37. The method of claim 27, further comprising:initializing the second protocol stack from a powered down state intoShowtime, wherein said bonding is executed in response to initializingthe second protocol stack into Showtime.
 38. The method of claim 37,wherein the second protocol stack is initialized into a Showtime lowpower state.
 39. The method of claim 27, wherein in a first mode saidbonding is not executed, wherein in a second mode said bonding isexecuted, wherein the method further comprises: switching between thefirst mode and the second mode during Showtime.
 40. The method of claim39, further comprising: in the first mode: the second protocol stackgenerating at least one of idle bits and synchronization symbols forcommunication on the second physical line.
 41. The method of claim 39,further comprising: in the first mode: operating the second protocolstack in a Showtime low power state or in a powered down state.
 42. Themethod of claim 39, further comprising: switching between the first modeand the second mode depending on at least one of a traffic load and atraffic throughput of the communication on the first physical line. 43.The method claim 39, further comprising: switching between the firstmode and the second mode at a point in time between two time-divisionmultiplex frames of the Physical Medium Dependent layer and/or at apoint in time corresponding to a synchronization frame of the PhysicalMedium Dependent layer, the synchronization frame corresponding to atleast one synchronization symbol.
 44. The method claim 39, furthercomprising: in response to switching between the first mode and thesecond mode: communicating control data at least one of the firstphysical line and the second physical line, the control data indicatinga parameter of said bonding.
 45. The method of claim 27, furthercomprising: modulating a sequence of bits output by the Physical MediumDependent layer of the first protocol stack into a multitone symboltransmitted on the first physical line, modulating a sequence of bitsoutput by the Physical Medium Dependent layer of the second protocolstack into a multitone symbol transmitted on the second physical line.46. A device, comprising: a first interface configured to communicate ona first physical line, a second interface configured to communicate on asecond physical line, at least one processor configured to implement afirst protocol stack for communication on the first physical line viathe first interface, wherein the at least one processor is furtherconfigured to implement at least parts of a second protocol stack forcommunication on the second physical line via the second interface,wherein the at least one processor is configured to bond the firstprotocol stack and the second protocol stack at the Physical MediumDependent layer of the first protocol stack and at the Physical MediumDependent layer of the second protocol stack.